/**
 * $RCSfile$
 * $Revision$
 * $Date$
 *
 * Copyright 2003-2007 Jive Software.
 *
 * All rights reserved. Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.jivesoftware.smack;

import org.jivesoftware.smack.packet.Presence;

import java.util.Collection;

/**
 * A listener that is fired any time a roster is changed or the presence of a
 * user in the roster is changed.
 * 
 * @see Roster#addRosterListener(RosterListener)
 * @author Matt Tucker
 */
public interface RosterListener {

	/**
	 * Called when roster entries are added.
	 * 
	 * @param addresses
	 *            the XMPP addresses of the contacts that have been added to the
	 *            roster.
	 */
	public void entriesAdded(Collection<String> addresses);

	/**
	 * Called when a roster entries are updated.
	 * 
	 * @param addresses
	 *            the XMPP addresses of the contacts whose entries have been
	 *            updated.
	 */
	public void entriesUpdated(Collection<String> addresses);

	/**
	 * Called when a roster entries are removed.
	 * 
	 * @param addresses
	 *            the XMPP addresses of the contacts that have been removed from
	 *            the roster.
	 */
	public void entriesDeleted(Collection<String> addresses);

	/**
	 * Called when the presence of a roster entry is changed. Care should be
	 * taken when using the presence data delivered as part of this event.
	 * Specifically, when a user account is online with multiple resources, the
	 * UI should account for that. For example, say a user is online with their
	 * desktop computer and mobile phone. If the user logs out of the IM client
	 * on their mobile phone, the user should not be shown in the roster
	 * (contact list) as offline since they're still available as another
	 * resource.
	 * <p>
	 * 
	 * To get the current "best presence" for a user after the presence update,
	 * query the roster:
	 * 
	 * <pre>
	 * String user = presence.getFrom();
	 * Presence bestPresence = roster.getPresence(user);
	 * </pre>
	 * 
	 * That will return the presence value for the user with the highest
	 * priority and availability.
	 * 
	 * Note that this listener is triggered for presence (mode) changes only
	 * (e.g presence of types available and unavailable. Subscription-related
	 * presence packets will not cause this method to be called.
	 * 
	 * @param presence
	 *            the presence that changed.
	 * @see Roster#getPresence(String)
	 */
	public void presenceChanged(Presence presence);
}